The present invention relates to an improved hot-blast stove of the type including an outer sheet or plate metal casing and an inner lining of insulating and refractory material as well as gas tight elements for blocking off the flow of gas toward the inner surface of the metal casing.
It is well known that the refractory lining of hot-blast stoves is not gas tight, such that gases which contain corrosive components may penetrate from the interior of the hot-blast stove to the inner surface of the metal casing and condense in such area. Condensate of this type causes corrosion which, together with the stresses present in the metal casing, leads to the so-called intercrystalline stress corrosion. This causes relatively rapidly occurring cracks and breaks in the metal casing.
German DT-AS No. 1,955,063 describes in detail the phenomenon involving intercrystalline stress corrosion and also suggests means of preventing the deposit of corrosive agents on the inner surface of the metal casing. According to this solution, a second, interior gas tight casing or lining of metal or heat-resistant synthetic resin is provided within the outer metal casing and is formed in the shape of the outer metal casing.
The purpose of the inner casing is to stop the gases penetrating toward the outer metal casing through the pores and leaks of the lining.
However, practice has shown that, e.g. under careless handling, improper placement, or during the operation of the hot-blast stove, the inner lining or casing may be broken, so that the gas-blocking effect thereof may be lost.